Overall Goals Our long-term objective is to delineate and characterize sperm-specific and seminal fluid components which may be involved in sperm survival in the female genital tract, and to ascertain their function. The results of these studies will expand our knowledge of the mechanisms of sperm survival and lead to new means of fertility regulation. Studies Conducted from September 1981 - June 1982: I. Nature of Selective Binding of Non-immune Immunoglobulins to Bull Spermatozoa: We previously reported the phenomenon of non-immune IgG and aggregated human globulin (AHG) binding to bull spermatozoa. Using an enzyme-linked immunosorption assay (ELISA), we now demonstrated that binding of immunoglobulin was selective for the Fc portion of IgG. IgM, IgA, and IgG-F(ab)'2 fragment did not bind to bull spermatozoa, but IgG, AHG, and IgG-Fc fragment did bind. Additionally, complement (which binds to the Fc portion of IgG) inhibited binding of IgG, AHG, and Fc-fragment to bull spermatozoa. Thus, binding of immunoglobulin to bull spermatozoa is selective for IgG and is mediated by the Fc portion of the IgG molecule. II. IgG-Fc Binding to Mammalian Sperm The phenomenon of IgG-Fc binding was examined with rabbit and human ejaculated spermatozoa and hamster epididymal spermatozoa. In each of these cases, binding of non-immune globulin was selective for IgG and binding was mediated by the Fc portion of the IgG molecule. The ELISA techniques used for these determinations confirmed that Fc-mediated binding was qualitatively similar with each of the mammalian spermatozoa examined and strongly suggested that IgG-Fc binding was a general property of mammalian spermatozoa. III. Nature of the IgG-Fc Binding component of Bull Spermatozoa We previously reported that the property of IgG and AHG binding to bull spermatozoa was retained in isolated bull spermatozoa membranes. In the previous year we examined the nature of this sperm surface binding component and found that it was unaffected by proteases, deoxyribonuclease, ribonuclease, and neuraminidase. Bull spermatozoa incubated for 12 hr at 37 degrees with trypsin, pepsin, papain, pronase, deoxyribonuclease, ribonuclease, or neuraminidase were not prevented from binding IgG qualitatively or quantitatively. Additionally, 0.5 percent (v/v) glutaraldehyde, 0.1 M acetic acid, 0.5 percent (v/v) NP-40, and 0.1 percent (v/v) Triton X-100 treatments of bull spermatozoa had no effect on subsequent binding of IgG to the spermatozoa. However, 50 mM dithiothreitol or 100 mM 2-mercaptoethanol treatment of bull spermatozoa reduced subsequent binding of IgG to spermatozoa by more than 50 percent. These findings implied that the binding component was unusually stable and was unlike the IgG-Fc receptor of lymphocytes (which was destroyed by neuraminidase and removed by nonionic detergents). Additionally, the sensitivity of the binding component to disulphide reducing agents implicated intact disulfides in the binding of IgG-Fc to the sperm surface.